Television: The case of the ailing, intellectual inspector remains open - only just

was never embarrassed about belonging to the tradition of the English murder mystery - cerebral, moving at its own pace towards the solution of some intricate problem, at which it would duly arrive on schedule, like the gent who manages to complete the crossword every morning just as his train pins into Waterloo station - so the similarity between The Wench Is Dead and Josephine Tey's The Daughter of Time was surely meant to be noticed.

In Tey's novel, Inspector Grant is in hospital applying his detective skills to the mystery of the Princes in the Tower. On Wednesday night, was in hospital re-examining the case of two men hanged for a murder in Victorian Oxford. The daughter of time, according to the old proverb, is truth; and the truth is what these erudite inspectors pursue, regardless of how far back in time it takes them.

While Morse was busy trying to right this historical miscarriage of justice, drawing on all the resources of the Thames Valley Police and the costume department (knickers, mid-Victorian, with slit crotch, one pair), his fans were more anxious about the results of the biopsy. Was he as sick as he looked? Would he be forced into early retirement? Sergeant Lewis had got his well-deserved promotion and was waiting to take the job. Chief Superintendent Strange was only too eager to send his too-clever inspector packing. Meanwhile, Morse had the services of a new assistant, PC Kershaw (played by Matthew Finney). Unlike Lewis, who used to be bemused by Morse's references to opera and Classical literature, and always had to ask how to spell "corroborate", Kershaw was a graduate of the University. In the search for the truth about the Tow-Path Murders, he was sometimes one step ahead of Morse himself; a bit of a smartarse, in fact.

This was fine for the episode, but could be bad for the series. The strength of Morse rests on a nice balance of opposites: knowledge and ignorance, analysis and intuition, Town and Gown, Oxford itself, a city with "too many scholars and not enough policemen", being presented repeatedly as a site of contrasts. Lewis ("wholesome, honest, unpretentious, humble," as Morse sees him in one of the books) is what people expect from a good copper - which is why Morse is constantly able to surprise them. In Colin Dexter's novels, his culture is more literary, while in the television series, the Inspector's intellectual superiority has been denoted chiefly by his love of opera, though he was certainly able to translate a Latin inscription or to cap a pretentious quote from time to time. Incidentally, in Dalziel and Pascoe, the equation is reversed: the older man being the bluff, honest copper and his younger assistant the educated one. In both series, the unexpressed feelings of these contrasting personalities for one another has been one of the main things that helped to captivate us.

John Thaw played the part with a finely judged air of cynicism, detachment and (where Lewis was concerned) obviously paternal affection. It is unlikely that he could ever convey the same mixture of pride and exasperation towards Kershaw, especially if the new man keeps on referring to Morse's beloved car as "nice wheels". Thaw brought to Morse some of the traits of character he had developed as Regan in The Sweeney and seemed to have realised himself so perfectly as the Oxford inspector that it has been hard to care much about the torments he appears to suffer as Kavanagh QC or to see his year in Provence as more than a frightful aberration.

If there was anything implausible about this middle-aged detective being so well acquainted with Plato and Puccini, able to tell a Seurat from a Cezanne and to articulate his feelings about the 1949 St Emilion, then Thaw convinced us. We believed, too, in the succession of women who continued to take a close interest in him, though the bodies that most seemed to excite him were those waiting for autopsy.

Was this the last episode? It was advertised as such, the 32nd in a series that has long since exhausted the possibilities of its characters and its setting. "So, it's the end, is it?" Morse's doctor asked, when the inspector announced he was considering early retirement. The reply was a guarded "I think so" - followed by an ambiguous remark about our ends being our beginnings. Perhaps this meant that the producers were keeping their options open, but almost certainly they would be best advised to call it a day.